The question Could someone tell me about good books about Hawaiian mythology? hasn't been closed.
I'm not sure why it hasn't been closed: it's a recommendation question and recommendation questions are fundamentally subjective. Do people want recommendation questions to be on topic here?
My two cents: What are good sources to introduce people to mythology? as a single source question was a good idea however at this point it doesn't cover everything so I think it's legitimate for people to ask about sources that are missing in this question.
Nothing prevents you afterwards to add what was missing to What are good sources to introduce people to mythology? to keep this one THE seminal answer to source questions and then vote to close the others as duplicate but you can't close them as duplicate beforehand since the information they request is not present yet. Or you can also not close those question and just add a link to them in What are good sources to introduce people to mythology?.
The paradoxal issue is that What are good sources to introduce people to mythology? is by essence an open-ended list (i. e. the kind people claim are not a good fit for SE Q&A model) whereas questions asking for sources for one specific mythology are not: many mythologies (like typically the hawaiian one) were studied only but a small, finite amount of scholars.
I think the existence of What are good sources to introduce people to mythology? encourages questions of this sort. I don't see how one can be defended and the other discouraged.
Last I saw, people wanted to see how these play out. Which is fine, and I don't think they have proven to be problematic here yet. Both of these seem to be well received enough, and the Hawaiian mythology question seems to have a reasonable answer.
If the day comes where we decide these need to go, What are good sources to introduce people to mythology? absolutely must be removed with all the rest. The rules apply to everybody, and exceptions encourage other people to behave similarly, and then get grumpy when they get punished for it (rightly so!).
So, to both of these questions:
